Efeitos do hipotireoidismo gestacional experimental na nocicepção supraespinhal na prole de ratos antes e após aplicação de morfina

Abstract

Thyroid hormones are essential for the adequate development of physiological systems, as the Central Nervous System. Thus, thyroid diseases may be responsible for neurological disorders in adulthood of offspring. Adequate serum concentrations of maternal thyroid hormones, especially at the first trimester of gestation, play an important role in ensuring adequate offspring development. This study aims to investigate the repercussions of experimental gestational hypothyroidism (EGH) on the supra-spinal nociceptive function and on the opioidergic circuitry of rats’ offspring. EGH was induced by adding 0.02% methimazole in drinking water from the ninth day of gestation until delivery. Male offspring of hypo (n=14) and euthyroid (n=14) mothers were submitted to baseline nociceptive threshold assessment at 60 days postnatal using a Hot Plate apparatus (52 ° C), by measuring the latency of the vigorous licking response of the hind paw. Subsequently, the animals received intraperitoneal injection of morphine (3 mg / kg) and were reassigned on the hot plate for nociceptive threshold evaluation at 30, 60, 90 and 120 min after the injection. The EGH did not affect the supra- spinal nociceptive threshold in the offspring. However, the use of morphine increases the nociceptive threshold at 30 and 60 minutes after injection of morphine (interaction factor: F (4,100) = 2.49, p <0.05). Thus, HGE does not affect the basal thermal nociception of the offspring but raises the sensibility to morphine. This result show that EGH can increase the expression or sensitivity in opioidergic receptors of pain modulatory circuitry.